In addition to aircraft propulsion applications, gas turbines are widely used particularly for power generation, a combustible gas/air mixture being ignited in the combustion chamber and the energy liberated by the exothermic reaction producing an expansion and/or pressure increase. The resulting combustion gases are fed to a downstream flow path of a turbine in order to convert the energy of the gas into mechanical energy, specifically rotational energy. The mechanical rotational energy obtained thereby can be used e.g. for generating electricity or propelling a ship.
With regard to the design of combustion chambers for gas turbines, two different approaches are basically known. On the one hand the combustion chamber is of annular design, ignited gas/air mixture being introduced from at least one, generally a plurality of burners, into the annular combustion chamber in which is it evenly distributed and passes in an annular flow in the direction of the stationary and rotor blades disposed radially around a rotor shaft in the turbine's flow path. On the other hand, combustion chamber arrangements having a plurality of individual combustion chambers, so-called cans, are known.
In order to achieve a high degree of efficiency for such turbines, taking into account the extreme physical requirements, combustion chambers and also burner inserts are often cooled. To achieve this, the cooling is often extracted from an existing coolant reservoir which is at the same time also a component of the combusting mixture. Specifically air which has been condensed before being fed to the combustion chamber is used for this purpose. This air simultaneously serves as a coolant. In order not to significantly impair the efficiency of the gas turbine by tapping off the cooling air, closed-circuit cooling systems are being increasingly used in which the air is returned to the combustion chamber after having performed its cooling function. This enables loss of air to be prevented and also allows the heat energy absorbed by the cooling air to be fed back into the process.
The disadvantage with this prior art is that closed-circuit cooling systems of this kind are very expensive to design and involve complicated assembly.